EPIC- Extracorporeal Photopheresis (ECP) for Immune-related Colitis

Inclusion Criteria: * Participants diagnosed with unresectable or metastatic melanoma or unresectable, advanced or metastatic NSCLC, who received ICI treatment with agents like anti-programmed death-1 (PD-1), anti-cytotoxic T-lymphocyte antigen 4 (CTLA-4), and had shown a response to the treatment, based on having a complete response, partial response, or stable disease determined by Response Evaluation Criteria in Solid Tumors (RECIST) 1.1 criteria. * Participants diagnosed with ir-colitis of at least Grade 2 severity based on American Society of Clinical Oncology (ASCO) Guidelines (diarrhea with an increase of ≥4 stools more than at baseline) with other causes of diarrhea and colitis ruled out. * Participants with endoscopy evidence of ir-colitis based on colonoscopy (modified Mayo Endoscopy Subscore of ≥2). * Participants with inadequate response to corticosteroids, defined as no improvement in ir-colitis after at least 72 hours of corticosteroid treatment, or relapse of ir-colitis during or after corticosteroid tapering. * Participants who have an Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 2. * Participants who may become pregnant must have a negative serum pregnancy test, agree to use effective birth control methods during the study and for 30 days after the last treatment, and not be breastfeeding. * Participants whose sexual partner may become pregnant, must use condoms or other effective contraception, and avoid donating blood, semen, or sperm during the study and for 90 days after the last treatment. * Participants must agree to wear UVA-absorbing, wrap-around sunglasses and cover exposed skin or use a sunblock (sun protection factor \[SPF\] ≥ 15) for the 24-hour period following treatment with UVADEX, whether exposed to direct or indirect sunlight. Exclusion Criteria: * Presence of irAEs and other than ir-colitis, with severity grade \> 2 based on ASCO guidelines. * Treatment of ir-colitis with any systemic therapy other than corticosteroids. * Concurrent conditions that might require treatment with corticosteroids ≥ 1 milligram per kilogram body weight per day (mg/kg BW/day) prednisone equivalent. * Concomitant treatment with any chemotherapy or targeted therapy for malignant melanoma, NSCLC, or other cancers. * Use of any investigational agent within 5 half-lives of the study treatment. * Contraindications to study interventions or procedures (UVADEX, the ECP procedure, infliximab, or vedolizumab). * Known allergic reaction to any component of the investigational agents, 8-methoxsalen (UVADEX), infliximab, or vedolizumab. * Presence of aphakia or history of light-sensitive diseases such as lupus erythematosus, porphyria cutanea tarda, erythropoietic protoporphyria, variegate porphyria, xeroderma pigmentosum, or albinism. * Inability to tolerate the fluid shift associated with the ECP procedure. * Positive test for human immunodeficiency virus (HIV). * Positive test for tuberculosis (blood test). * History of prior allogeneic bone marrow or solid organ transplantation. * Previous or current malignancies within the last 3 years, other than unresectable or metastatic melanoma or unresectable, advanced, or metastatic NSCLC treated with ICI. Exceptions include adequately treated basal or squamous cell skin cancer. Note: Other Inclusion/Exclusion criteria also apply.